After applying IR-informed priors to X-ray NH posteriors in a sample of 811 high-z AGN, CTK sources comprise 17% of the population at 3<z<6 with no significant evolution.
The Accretion History of AGN I: Supermassive Black Hole Population Synthesis Model
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abstract
As matter accretes onto the central supermassive black holes in active galactic nuclei (AGN), X-rays are emitted. We present a population synthesis model that accounts for the summed X-ray emission from growing black holes; modulo the efficiency of converting mass to X-rays, this is effectively a record of the accreted mass. We need this population synthesis model to reproduce observed constraints from X-ray surveys: the X-ray number counts, the observed fraction of Compton-thick AGN [$\log$ (N$_{\rm H}$/cm$^{\rm -2}$) $>$ 24] and the spectrum of the cosmic X-ray background (CXB), after accounting for selection biases. Over the past decade, X-ray surveys by {\it XMM-Newton}, {\it Chandra}, \textit{NuSTAR} and \textit{Swift}-BAT have provided greatly improved observational constraints. We find that no existing X-ray luminosity function (XLF) consistently reproduces all these observations. We take the uncertainty in AGN spectra into account, and use a neural network to compute an XLF that fits all observed constraints, including observed Compton-thick number counts and fractions. This new population synthesis model suggests that, intrinsically, 50$\pm$9\% (56$\pm$7\%) of all AGN within z $\simeq$ 0.1 (1.0) are Compton-thick.
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Using ray-tracing simulations and simulation-based inference, the authors construct an AGN population that reproduces the cosmic X-ray background, number counts, and absorption properties, deriving an intrinsic Compton-thick fraction of 40±3%.
Higher Eddington ratio AGN exhibit increased [O III] outflow incidence and reduced obscuration, supporting radiative feedback as the regulator.
X-ray analysis of 94 FIR-selected AGNs at z=0.07-5 shows rising obscured fraction with redshift, soft excess in 10 sources, and a luminosity-dependent covering factor correlation supporting the receding torus model.
SKAO continuum surveys will detect radio emission from JWST AGN and LRDs and distinguish between Compton-thick absorption, intrinsically weak accretion, and dense gas cocoon scenarios.
Overview chapter summarizing traditional orientation-based and radiation-regulated unification models for AGN, including evolutionary aspects and changing-look AGN.
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Population synthesis of active galactic nuclei based on the radiation-regulated unification model
Using ray-tracing simulations and simulation-based inference, the authors construct an AGN population that reproduces the cosmic X-ray background, number counts, and absorption properties, deriving an intrinsic Compton-thick fraction of 40±3%.